During a swing made by a golfer, the golf club is subjected to deformation such as deflection and torsion in the shaft thereof. In addition, the club head turns over, and the head speed undergoes change as well. Such behaviors of the golf club, including the deformation of the shaft, the turning of the head, and the change in head speed, all result mainly from inputs that are made by a subject, such as a golfer, making the swing. It is considered extremely important for a golfer to select a golf club capable of attaining an ideal behavior of the golf club.
Therefore, it is very useful to analyze a golf club behavior during a swing, in order for a golfer to select an optimum golf club from among ready-made golf clubs. Further, information to be obtained as a result of such analysis is significantly effective in developing a new golf club.
As a method of analyzing the behavior of a golf club during a swing made by a golfer, there has been hitherto proposed a method of simulating a swing, which involves calculating, from the chronological change of the grip of the golf club on three-dimensional coordinates during the swing, input information on parameters for use in the simulation (see, for example, Patent Literature 1). In this method, a swing can be simulated based on three motions including: a translational motion relative to the global coordinate of the grip; a rotary motion relative to the global coordinates; and a rotary motion (torsion) of the grip about the geometrical center axis of the shaft, the three motions being obtained from the chronological change of the three-dimensionally measured grip coordinates.